Systems such as “Apple TV” are well known. Apple TV is a digital media receiver designed and sold by Apple, Inc. It is a networked device intended to play digital content such as audio and/or video provided from any associated Macintosh or Windows client type computer. Typically the client computer is one executing the “iTunes” client. The Apple TV connects to the client computer (which is connected to the Internet for receipt of the video) and stores and plays the video, for instance, on an enhanced definition or high definition television. The Apple TV device stores content which are the audio or video files on an internal hard disk drive. The Apple TV device connects to a television or other video equipment, for instance, through high definition multimedia interface (HDMI) or component video connections. The Apple TV is somewhat similar to the Apple iPod. It is paired with an iTunes library on the client computer and can synchronize with that library, copying content to its own hard disk drive. Thus Apple TV and similar products allow one to obtain, for instance, video materials such as television programs or movies, from an online “store” such as the iTunes Store operated by Apple, Inc. Other such stores also exist. The material provided may be in the form of a download or streaming video or audio. Typically the connection with the store is via the Internet. Of course, other similar products are available which may be integrated with a computer, or are dedicated devices not requiring a general purpose computer but providing the same functionality of obtaining video and audio content via the Internet such as the Apple Inc. “iPhone.”
Typically the content provided is protected against misuse. A typical means of this protection is encryption. That is, material as provided to the Apple TV or similar client device is encrypted. A decryption key is conventionally provided so that the material may be decrypted. Managing the keys is a significant technical problem. Obviously if all instances of the downloaded or streamed material have the same key for all users, this is not secure enough since the key could be publicly available. Thus some form of key management is typically provided.
However, satisfactory forms of key management are problematic especially given a large number of users and hence a large number of keys being required. While encryption security in this context need not be airtight, a certain degree of security is necessary since audio and video content have to be protected against hacking.